Italy's Francesco Bagnaia, riding a Ducati, claimed his third successive MotoGP pole position of the season at the Grand Prix of the Americas on Saturday as he continued to revel in his title duel with France's Fabio Quartararo.
Bagnaia also ended six-time world champion Marc Marquez's run of seven successive poles at the Texan circuit.
World championship leader Quartararo, on a Yamaha, and Honda's Marquez complete the front row for Sunday's race, the 15th of the season.
Quartararo, 22, bidding to become France's first MotoGP world champion, has won five races this year and has a 48-point lead over Bagnaia.
However, the in-form Italian has captured the last two races.
"I really enjoyed my qualifying round because I wasn't expecting it," said the 24-year-old.
"I'm very happy. It's very important to start first."
Saturday's qualifying at the Circuit of the Americas had been overshadowed by anger over the state of the track which will also host a Formula One race in three weeks' time.
In Friday practice, Quartararo was particularly unhappy with bumps that have appeared on the track, particularly on Turns 2, 3 and 10.
"It looks like a motocross training ground," Quartararo said. "It's barely acceptable to race on... and dangerous."
On Saturday, he admitted he was still getting to grips with the surface.
"I had a little more difficulty than usual in qualifying," he said.
"But it's always great to start on the front row. We'll see what we can do but our pace is not bad."
Marquez won the first six races staged at the Austin circuit but fell off while leading in 2019.
The event was cancelled last season when he was recuperating after breaking his right arm in a crash.
He returned this season and, while he is clearly not 100 percent, he has been much stronger at the few counter-clockwise circuits, like Austin, which put less pressure on his right arm.
Sunday's front row start will be his first since his return to the sport.
"I am very happy with the front row because it's been one of my weak points this season," said Marquez.
"It's my first in 2021 which feels strange to say but that's what it is."
As well as Quartararo and Bagnaia, three other men still have slim, mathematical chances of lifting the title.
France's Johann Zarco was sixth fastest on Saturday on a Ducati-Pramac with defending champion Joan Mir, on a Suzuki, in eighth and Ducati factory rider Jack Miller of Australia only qualifying 10th.
Miller had been the fastest man on the track in practice in the morning.
Aprilia rider Maverick Vinales, whose 15-year-old cousin Dean Berta Vinales was killed in a race in Jerez last weekend, opted not to race in Texas.
In Moto2, Spain's Raul Fernandez on a Kalex starts from pole while compatriot Jaume Masia, riding a KTM, was the fastest qualifier in Moto 3.